Technical Field
The present invention relates to a photopolymerizable inkjet ink, an ink cartridge containing the ink, photopolymerizable composition and a coated matter therewith.
Description of the Related Art
PCT Japanese published national phase application No. 2004-526820 discloses a photopolymerizable composition and a photopolymerizable inkjet ink using (meth)acrylic acid ester.
However, many of monomers used in conventional photopolymerizable inkjet inks have toxicities. Particularly, inexpensive and easily-obtainable (meth)acrylic acid esters occasionally cause allergies when contacting skins.
It was found that some (meth)acrylic acid esters and (meth)acryl amides cause less skin sensitization. For example, as disclosed in Japanese published unexamined application No. JP-2012-140593-A, methacrylate is less toxic than acrylate and suggested an inkjet ink mainly using methacrylate.
The inkjet ink is required to have low viscosity even when including various materials such as a pigment and an additive so as not to prevent the ink from ejecting. Water can be included therein to lower the viscosity and the photopolymerizable inkjet ink including water is known. However, since penetration drying cannot be expected from non-permeable substrates as mentioned later, a process of vaporizing water is needed for higher processing speed and efficiency, resulting in enlargement of the apparatus.
When the photopolymerizable composition is used for brush coating, an organic solvent can be used. Since the organic solvent is volatilized and discharged in the atmosphere, the organic solvent is preferably used in a minimum amount in consideration of influence on the environment. On the other hand, when used as an inkjet ink, the organic solvent having high volatility occasionally increases viscosity of the ink, resulting in poor rejection thereof. The organic solvent needs adjustment in volatility for the ink to stably eject.
In some cases, on a chassis or a molded product, a metallic layer such as aluminum or stainless is formed to impart metallic gloss thereto for the purpose of improving design. In such case, a thin film may be formed on the metal surface to protect the surface, for example, to prevent the surface from eroding. However, conventional photopolymerizable compositions are difficult to adhere to the metal surface. Then, a new photopolymerizable composition including methacrylic acid ester having a phosphoric group has been disclosed in Japanese patent application No. 2013-91979.